798 Proceedings of Royal Society of Edinburgh. [sess. 
than during the rest of the year, the difference was not very 
marked. 
The distribution of Pseudocalanus, on the other hand, showed 
a fairly distinct variation in the larger numbers obtained during 
the earlier and later months of the year than during those of 
summer. It occurred in considerable numbers from January till 
the end of March ; but after that the numbers became fewer, till 
about the beginning of* September, when there was again a per- 
ceptible increase that continued till December. 
The distribution of Acartia Clausi exhibited changes somewhat 
similar to those of the Pseudocalanus , but the changes were 
scarcely so well marked ; it also appeared to become proportionally 
more plentiful from the end of August till the beginning of 
October than at any other time during the year. 
Paracalanus parvus (No. 2 in the table). — This species was 
present in every sample from January till about the middle of 
April, but from that time till the beginning of July it was only 
observed once, and for the remainder of the year its appearance 
was more or less irregular. 
Centropages hamatus (No. 9). — This species, in curious contrast 
to the Paracalanus , was observed in none of the samples till about 
the middle of March ; but after that time it occurred, though at 
first very sparingly, in nearly every sample collected, till about the 
middle of November, when no more specimens were noticed. 
The distribution of Temora longicornis (No. 11) was somewhat 
similar to that of the Centropages. Like that species, it appeared 
to be entirely absent during the early part of the year. It was 
noticed for the first time in the sample collected on the 19th of 
March ; but thereafter it occurred at intervals, and for the most 
part very sparingly, till near the end of June it then occurred 
more regularly, though still in limited numbers, till the beginning 
of October, when it became more scarce and intermittent in its 
appearance. 
The only other species present more or less throughout the year 
was Oithona similis (No. 18), and its distribution was somewhat 
similar to that of Acartia , except that it was absent in nearly all 
the samples collected in April, and in half of those collected in 
May and June. 
